There are several types of unwanted or unnecessary passageways within the body. Very often these passageways are not only unnecessary, they are also harmful. Unnecessary passageways in blood vessels or in the heart can be especially harmful, since they can cause the reduction of blood flow, or the bypass of blood flow around an organ. When unwanted passageways exist, they often are congenital in origin, and their correction must often be undertaken in infants. This makes conventional surgical procedures more troublesome, because of the small size of the vessels, because of the additional risk involved in anesthesia, and because other birth defects are often also present.
By way of example, a common type of congenital defect is patent ductus arteriosus, in which an unwanted passageway or duct connects the aorta to the main pulmonary artery, close to the heart. This defect results in the recirculation of oxygenated blood through the lungs, depriving the other organs and tissues of part of their required blood flow. Increased work for the heart results, and enlargement of the heart often ensues.
Surgical correction of patent ductus arteriosus requires entry into the thoracic cavity, usually through the side, involving considerable trauma to the surrounding musculature and connective tissue. Surgery also involves considerable risk, because of the necessity of clamping the duct next to each of the major arteries, and because of the risk of failing to suture the duct successfully. In infants, the duct material is often fragile, and permanent suturing is especially difficult. Even small injuries to surrounding tissues can be extremely serious, and unexpected complications can happen quickly and accelerate rapidly. In this particular defect, surgical correction also always involves the manipulation of a nearby nerve, with the attendant risk of nerve damage.
Other devices have been devised to occlude the unwanted passageway without thoracic surgery, with some success, but all such devices have suffered from the tendency to become dislodged from the passageway. If a device becomes dislodged, in attempting to correct this particular defect, the device will enter the pulmonary artery and lodge somewhere downstream, requiring surgical removal. Typically, such closure devices are advanced, on the end of a wire, either through a femoral or umbilical artery to the aorta, or through a femoral or umbilical vein and through the heart to the pulmonary artery. Guide catheters and guidewires for installing such devices are well known in the art, as are the methods for their use. Once advanced through either the artery or the vein to the ductus arteriosus, the closure device is positioned in the duct and attached in place by some mechanism.
One such known device is a conical foam plug stabilized by an inner steel frame. Another device is a double umbrella type spring loaded wire frame covered by two foam discs. Still another device is a grappling hook device. All of these devices are deployed within a tube of some kind and allowed to expand in place in the passageway by being pushed or pulled out of the tube. Expansion is accomplished either by means of spring action or by manipulation of the wire. Many known devices are held in place by clotting in the closure material, combined with some kind of spring action pressing against the walls of the passageway.
While achieving some success, each of the known devices still becomes dislodged in a fairly high number of cases. There are several underlying reasons why the known devices are not able to permanently block the passageway, in many cases. First, in a defect of this particular type, as well as some others, the flow of blood through the unblocked passageway can be at a relatively high velocity, resulting in some damage to the endothelial tissue surrounding at least one end of the passageway. Second, the passageway can also often be attached to the arteries at a slight angle. These problems, as well as others, can result in a less than optimum sealing surface for the closure device. Unfortunately, most of the known devices attempt to seal along a relatively small surface area, often almost along a line of contact. For example, the double umbrella device, as well as other disc type sealing devices, requires a fairly smooth sealing surface to be successful, and optimally the duct should be attached at right angles to the arteries. Lacking a smooth sealing area around the mouths of the passageway, especially where an oblique angle exists, use of this type of device often results in unwanted residual flow through the shunt, often in the form of high speed jets.
Another problem which besets the known devices is the inadequacy of the outward force generated by the spring devices, in first achieving sealing, and ultimately in maintaining a seal long enough to allow thrombosis to complete the seal. This is true whether the device relies on a coil spring or some other type of spring device for the spring force.
Therefore, it is an object of the present invention to provide a body passageway closure method and apparatus which will provide a large sealing area in a passageway, and which will avoid the rough areas surrounding the ends of the passageway. It is a further object of the present invention to provide a body passageway closure method and apparatus which will seal against the walls of the passageway by means of a sufficiently high force to embed significant portions of the apparatus into the walls of the passageway to retain the apparatus in place. It is a still further object of the present invention to provide a body passageway closure method and apparatus which will permanently deform a portion of the apparatus to create a stable diameter pressed against the walls of the passageway, to result in a secure attachment of the apparatus to the passageway. It is a yet further object of the present invention to provide a body passageway closure method and apparatus which will be easy to implement and relatively economical to manufacture.